Heretofore, as magnifying and observing instruments or devices there have been used, for example, microscopes and magnifiers. But in the case of a microscope, it is necessary to process an object to be observed and then take it to the microscope side. On the other hand, in the case of a magnifier, it is possible to take the magnifier itself to an object side to be observed and observe the object without applying any processing thereto; however, the magnification is low.
With such circumstances as background, the applicant in the present case has previously developed a magnifying and observing system having both the merit of high magnification of the microscope and the merit of handiness of the magnifier (Japanese Patent Laid Open No. 308527/89, Japanese Patent Application Nos. 26462/89 and 273419/89, U.S. Pat. Nos. 4,930,851 and 4,988,158).
The magnifying and observing system comprises a system body (not shown) composed of a monitor display and a controller, and an image pick-up apparatus (a lens barrel and a light condensing guide which are referred to in Japanese Patent Laid Open No. 308527/89) 100 shown in FIG. 13. The image pick-up apparatus 100 contains a magnifying and focusing optical system 102 and also incorporates therein optical fibers 103 for conducting into the apparatus an illuminating light to illuminate an object M to be observed from a light source provided on the system body side. The image pick-up apparatus 100 is further provided at a front end thereof with a light condensing guide 105. While the image pick-up apparatus is held by hand, the light condensing guide 105 is brought into abutment with the object M or is drawn close thereto, then an image obtained by an imaging device (a solid-state image sensing device) 104 incorporated in the image pick-up apparatus 100 is reproduced on the display and observed. The image pick-up apparatus 100 is constructed so that the focus is sure to be taken automatically when a front end of the light condensing guide 105 is brought into abutment with the object M or drawn close to the object up to a predetermined distance. Anybody can make observation at a magnification of fifty to several thousand diameters without the need of any skill or practice.
In such magnifying and observing system, however, a light source is disposed within the controller for obtaining a stronger illuminating light, which is conducted from the light source to the image pick-up apparatus through optical fibers. A control circuit unit interposed between the imaging device and the display for reproduction is also provided within the controller. Thus, the controller is needed in addition to the image pick-up apparatus and the display, resulting in increase in size as a whole. This point causes dissatisfaction in the case where a greater importance is attached to handiness.
The magnifying and observing system disclosed in the foregoing Japanese Patent Laid Open No. 308527/89 or No. 26462/89 or Japanese Patent Application No. 273419/89, the image pick-up apparatus is provided with an illuminating means, as noted previously, and an image of an object observed is taken in while the object is lighted by the illuminating means, then it is reproduced on the display provided on the system body side and is observed. Therefore, it is possible to make a stand-free observation, that is, carrying the image pick-up apparatus by hand up to an object to be observed and then making observation while keeping the object in place.
In such observation system, however, the light source for illuminating an object to be observed is formed by optical fibers, as mentioned above. More particularly, light is conducted through a bundle of optical fibers from the external light source, and front ends of the optical fibers of the bundle are arranged annularly to form an internal light source. The formation of such an internal light source can afford a stronger and uniform illuminating light, but requires the external light source, or the construction of the image pick-up apparatus becomes complicated. Besides, since expensive optical fibers are used, an increase of cost is unavoidable. Further, a very strong external light source is needed because there occurs propagation loss.
Also in Japanese Patent Application No. 224327/90 (Laid Open No. 107411/92) there is shown an example of a magnifying observation apparatus. This system has been developed for making the magnifying observation apparatus disclosed in the foregoing Japanese Patent Laid Open No. 308527/89, or Japanese Patent Application No. 26462/89 or No. 273419/89 smaller in size and easier to handle. To this end, several improvements are made therein.
One of the improvements resides in a construction wherein not only an imaging device but also a control circuit unit for controlling the imaging device is incorporated in an image pick-up apparatus of the observation system in question. Another improvement resides in that a front end portion of the image pick-up apparatus is bent sideways with respect to the body portion so that it can be handled in a direction which permits easy observation. At the same time, a reflecting mirror is used to change the direction of image light from an object observed. This is owing to the circumstances that since the imaging device is integrally connected with the control circuit unit, a light sensing surface of the imaging device cannot be made directly perpendicular to the direction of image light incident from the sideways-bent front end portion of the image pick-up apparatus. Thus, the structure using a reflecting mirror is not always desirable. The use of a reflecting mirror results in increase in the number of parts and a more complicated structure. Moreover, for example, in the case of using a polarized light, the polarized light is disturbed by the reflecting mirror, so that an accurate observation is impaired.
Further, all of the observation apparatus referred to above involve troublesomeness such that the replacement of optical system is necessary each time the magnification is to be changed.
The use of a magnification-variable optical system having a fixed focal plane is a solution to avoiding such troublesomeness, but those known heretofore as such magnification-variable structure are not suitable for stand-free observation systems. In more particular terms, a zoom lens is a typical example of such magnification-variable structure, but the principle thereof is such that a focal length is changed continuously by changing a mutual spacing of plural constituent lenses. Its design and structure are complicated and an increase in size of the optical system used therein is unavoidable. Thus, the zoom lens is not suitable to an observation system for stand-free observation in which simple structure and small size are ideal.
The present invention which has been accomplished under the above-mentioned background aims at attaining a reduction in size and handiness to a greater extent than in the conventional magnifying observation apparatus having such basic structure as referred to above.
It is another object of the present invention to provide a magnifying observation apparatus having a structure which does not require the use of optical fibers.
It is a further object of the present invention to provide a structure of an image pick-up apparatus having a front end portion bent sideways with respect to a body portion thereof which structure does not require the use of a reflecting mirror for focusing an image light incident from the bent front end portion onto a light receiving surface of an imaging device.
It is a still further object of the invention to provide a simple magnification-variable structure, namely, a simple zooming structure, suitable to an observation system for stand-free observation.